2 stroke twin cylinder turbo build

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DaveyG
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2 stroke twin cylinder turbo build

Post by DaveyG » Thu Mar 21, 2019 8:37 pm

Hey all, newb here. I stumbled upon this site by looking for microsquirt type stuff on eBay, I found a Franken board on there said something about rusefi.com so I searched and here I am! I’m in the middle of a crazy build trying to convert a 2 stroke twin to EFI and turbo it and I’m super cheap so I found some ITBs from another, larger displacement snowmobile, along with quite a bit of its wiring harness and sensors, and I understand the concepts pretty well, as far as tuning and fuel maps go, and I’m not afraid to solder, I’ve built several LiFePo4 battery packs with BMS boards and such, as well as a few other fun projects. I’m a machinist and fabricator by trade, do a good bit of stuff with CAD and the like. Here’s a rough pic of what I’m trying to build around my engine. Anybody on here have any experience with small engines? This is going on an Austrian built Rotax 670cc engine.
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DaveyG
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Thu Mar 21, 2019 8:44 pm

This is a pic of the same brand and model of throttle bodies I will be using. From an 800cc twin 2 stroke. Can see the injectors as well as the TPS sensor.
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russian
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Re: 2 stroke twin cylinder turbo build

Post by russian » Thu Mar 21, 2019 8:46 pm

Hello and welcome! https://rusefi.com/wiki/index.php?title ... ent_Status has links to http://rusefi.com/forum/viewtopic.php?f=3&t=396 and viewtopic.php?f=3&t=1322 - one is in Russian but the other one is not :)
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kb1gtt
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Re: 2 stroke twin cylinder turbo build

Post by kb1gtt » Thu Mar 21, 2019 11:30 pm

What is your alternator / magneto 12v generation capability? Most small engineers have a limited electrical budget. Do you have enough electrical power?

What is your fuel pump? How many amps does it draw?

What crank sensor are you planning for? Also Hall, VR, optical, other?

Most 2 strokes are tuned mechanically. I don't know if a turbo will provide hp like it will with a 4 stroke. First things first, make it EFI. Then think turbo.
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Fri Mar 22, 2019 1:13 am

Yeah planning on just doing EFI conversion first then doing turbo later. The fuel pump is just a cheapo in-line 190gph 45-90 psi unit, will need to run a separate return line to tank. I’m thinking I’ll run a hall-effect sensor, unless anyone suggests otherwise for simplicity reasons...? I plan to swap the factory stator for a later model stator from an electric start 670 that has a higher amp output, and also a battery, I’ll run a LiFePo4 10Ah battery pack for weight saving (and higher amperage) vs a lead acid.

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russian
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Re: 2 stroke twin cylinder turbo build

Post by russian » Fri Mar 22, 2019 1:22 am

https://rusefi.com/s/howtocontribute
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DaveyG
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Fri Mar 22, 2019 3:33 am

Ok so the Sachs build has me convinced. I gotta do this. So what hardware do I need to streamline the process, the STM32 board? Or should I get the Frankenstein board? Do I need both? Just watched a YouTube video about setting up rusefi with a STM32 board to start with.

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Re: 2 stroke twin cylinder turbo build

Post by russian » Fri Mar 22, 2019 3:39 am

If you go Frankenstein you need both.

If you go with another board you have options - see comparison at https://rusefi.com/wiki/index.php?title ... e:For_Sale
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kb1gtt
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Re: 2 stroke twin cylinder turbo build

Post by kb1gtt » Fri Mar 22, 2019 8:27 am

About fuel pump, see some of my older efforts noted here.

http://jaredharvey.com/Files/projects/E ... blower.htm

Hall or VR should be fine. Hall is perhaps a bit easier to do if you are making your own. VR is a bit more sensitive to making sure you have your magnetic fluxes correct. However both are fairly close in level of complexity to accomplish. Hall can have jitter issues, while VR can have magnetic flux issues.
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Mon Mar 25, 2019 5:36 pm

So can I get a Frankenstein board that is already assembled? Or are they only available if I do all of the soldering? I’m pretty good at soldering but that looks like a lot of points to do, and possibly cross circuits with my rudimentary soldering tools at my disposal. What does the Frankenstein board do that cannot be done with a STM32 board alone? Or with my skill level should I just jump straight to a pre-assembled Frankenso board? Could I just program an Arduino board to accomplish the same goals?

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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Mon Mar 25, 2019 5:45 pm

So I’m actually leaning toward the Frankenso pnp setup, with pinout already installed, comes to $384? Will that work with an EGT instead of an O2 sensor since my project is 2 stroke? What about the lack of MAF or MAP sensor? I could add a MAF to the system before the TBs rather easily but a MAP would be more difficult to plumb I think, as the TBs are pretty much bolted right to the crankcase (just a very short rubber boot) and making my own hall-effect sensor will be fairly easy, as I have a milking machine and a rotary table.

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Re: 2 stroke twin cylinder turbo build

Post by russian » Mon Mar 25, 2019 5:55 pm

No assembled Frankenstein for sale as far as I know

stm32 or arduino is brain, Frankenstein or Frankenso or else is body/muscle. rusEfi only works on stm32f4 or stm32f7. https://speeduino.com (no affiliation with rusEfi) works only on arduino

You need either TPS or MAF or MAP. So far no one has used EGT with rusEfi but the code is known to work on a test gas stove.

I am available to answer a lot but definitely not all questions :( There is a bit of a community here to help but you would have to do a lot of work on your own.
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Mon Mar 25, 2019 7:39 pm

Ok seems like rusefi has a bit longer track record, and more functional vehicles completed, than speeduino. How could I cut costs versus buying pnp Frankenso? Would I need to buy the pnp Frankenso AND a separate STM32 or does a STM32 come in the $384 pnp Frankenso package deal?
Last edited by DaveyG on Mon Mar 25, 2019 7:45 pm, edited 1 time in total.

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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Mon Mar 25, 2019 7:45 pm

If I get the ‘assembled Frankenso’ for $290, I need to add my own STM32F4 and LCD to be equivalent to the ‘pnp Frankenso’? Am I correct in that thinking?

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Re: 2 stroke twin cylinder turbo build

Post by russian » Mon Mar 25, 2019 7:57 pm

I believe options on the right would allow you to add stm32 but not add case and lcd

Frankenso is an overkill for you for sure but thats the only assembled rusefi option i am aware of. Frankenstein assemle yourself is for sure cheaper but you have to assemble it.
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Re: 2 stroke twin cylinder turbo build

Post by kb1gtt » Tue Mar 26, 2019 1:09 am

Your tugging at my heart strings. I've been wanting to make a small ECU for some time, but will not have time to consider it for a month or two.

Do you know of a MAF that works with 2 stroke? I expect 2 stroke to have a bunch of forward and backwards pulsations. This often confuses the MAF, tricking it to claim more O2's are in the cyl than reality. With MAP you can get more options in how you determine the air in the cyl. MAF is typically handy for low air flow, so low power.

With a mill, you could probably MFG an enclosure.

About EGT's, did you notice there are some EGT's on the PCB. Those are not typically populated, but should work. I'm kind of surprised that we don't see them being requested more often. I think the key problem with them, is that the software doesn't exist behind them. I think they can fairly easily be used as a gauge, or logged. However other feature like limiting power due to over temp, or triggering a check engine light, or other feature(s) are probably lacking a this point. If you populate the chips and start using it as a gauge, I'd bet @ would be willing to develop other EGT features.
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Tue Mar 26, 2019 5:33 am

With the standard Frankenstein build it yourself kit, how many pieces are there? If I buy that, what other parts will I need to purchase separately? My thoughts with EGT, is that it could work roughly like a rich/lean sensor, if I set a target temperature for stoich, it should be within a range of temperature, too high it is running lean, too low, running rich. Not nearly as accurate as a wide band o2 sensor I’m sure, but probably close enough for what I’m trying to accomplish. I think that is how manufacturer EFI 2-stroke engines use them (example is Arctic Cat 600/800 EFI snowmobile, the M800 is my main parts donor I wish to use for throttle bodies, fuel pump, EGT, and TPS)

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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Tue Mar 26, 2019 1:37 pm

This video (posted yesterday) has me thoroughly convinced that I can pull off the Frankenstein build without trouble. I was a bit concerned about doing the fine pitch pin chips, but his method seems easy enough. I’ve not done a ton of pcb soldering, but enough to be able to pull this off I think.

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Re: 2 stroke twin cylinder turbo build

Post by russian » Tue Mar 26, 2019 1:58 pm

Have you noticed that this video was posted yesterday? Thank you for the great find!
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DaveyG
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Tue Mar 26, 2019 3:44 pm

I’ve subscribed to that guy’s channel on YouTube. I’m looking forward to the next steps he takes with it. He is very thorough.

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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Tue Mar 26, 2019 8:53 pm

Well down the rabbit hole I go... I just ordered the Frankenstein kit with STM32 and resistor package.

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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Sat Apr 06, 2019 4:18 am

My RusEFI package arrived today!!!!! Unfortunately I had to take a short trip out of town immediately after I checked the mail and don’t even want to open the box until I’m back home and can lay everything out on my workbench. But I’m giddy like a little schoolgirl!

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Re: 2 stroke twin cylinder turbo build

Post by OrchardPerformance » Mon Apr 15, 2019 6:21 pm

I can't recommend getting solder paste enough, the stuff I have is Microprint from Warton Metals which if you are EU should be easy enough to get (while we are still in the EU :roll: ) but any other solder paste makes the process a lot neater and easier.

Even if you use an iron to put the components down and not hot air its still easier on those large multi pin chips as you can apply it much more neatly and then just heat.

It has the dual advantage of being more precise to apply and already containing the flux needed. It also leaves a hand free to hold the chip down if you cant/don't want to clamp.

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Re: 2 stroke twin cylinder turbo build

Post by kb1gtt » Mon Apr 15, 2019 9:31 pm

I agree paste is the way to go. Get it in a srynge and you soldering will get much better.
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Re: 2 stroke twin cylinder turbo build

Post by DaveyG » Wed Aug 14, 2019 2:56 pm

Still thinking of doing this but it got pushed to the back burner for the time being as higher priority projects have taken over. As for pulses my particular engine should have significantly lower amounts of reversion as it uses a rotary valve to keep the flow going in one direction, much more controlled than a reed valve or piston port 2 stroke. Also the reason it would be a good candidate for turbocharging, lesser chance of pressurizing the wrong cylinder.

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